Retrofit solutions allowing the use of light emitting diode (LED) devices in existing modules and fixtures for tubular lighting (TL) is an increasingly attractive alternative in order to improve the power efficiency of existing lighting systems.
To achieve a retrofit lighting device, it is known to arrange an LED module inside a sealed glass tube. In such a device, the inner surface of the glass tube is commonly coated with a phosphor material for wavelength conversion of light emitted from the LED device which tends to be towards the blue region of the visible spectra. Furthermore, it has been found that it is advantageous to use organic phosphor materials which have been shown to exhibit an increased lifetime compared to previously used wavelength converting materials. However, organic phosphors are sensitive to ambient air and it has been shown that organic phosphors in a sealed environment have a markedly longer lifetime. Therefore, it is important that the glass tube is properly sealed.
Known methods for sealing a glass tube for tubular lighting applications include standard lamp sealing techniques requiring an annealing step. Such an annealing step may result in that the surface of the lamp is heated over a large area. However, high temperatures treatments are not compatible with organic phosphor polymers. In an alternative approach, the glass tubes may be sealed by gluing a cap to the end of the tube. A drawback of the glued seal is that it is not as air-tight as a glass seal and the increased complexity of such a manufacturing method makes the glued seal less suitable for mass production.
Accordingly, there is need for a tubular lighting LED retrofit device and an improved method for manufacturing such a device facilitating the use of organic phosphorus materials.